Periodontal disease afflicts over an estimated 90 percent of the world's population. Lassari, E.P., Dental Biochemistry, 191-3, (1976). Although this disease is not life threatening, it often results in serious discomfort and tooth loss. The basic cause of this disease is bacteriological in nature. Both topical and systemic bactericidal agents have been found effective in combating the disease. Biological Basis of Periodontal Maintenance Therapy, G.C. Armitage, Proxis Publishing Company, 1980, pp. 34-78.
Recently, it has been demonstrated that combinations of various salts and hydrogen peroxide solution, when properly applied as part of a treatment under the supervision of a dentist, are effective in controlling periodontitis. B.G. Rosling et al., Journal of Clinical Periodontology, Vol. 10 pp. 487-514, 1983. Sodium bicarbonate, a particularly convenient and palatable non-toxic salt, is believed to be effective in this treatment. Keyes P.H. et al,, Quintessence International No. 1, January 1978, report 1590, pp. 51-56 and No. 2, February 1978, pp. 69-75.
The bacteria causing periodontal disease are anaerobic. Armitage, G.C., Biological Basis of Periodontal Maintenance Therapy, 1980. By providing high levels of oxygen, hydrogen peroxide is believed to be effective in killing these bacterial organisms. Hydrogen peroxide is the preferred oxidizing agent as it is readily available, proven effective and non-toxic.
In addition to treating periodontal disease, many individuals like to use baking soda and peroxide to clean their teeth. Several of the benefits cited by those using this combination include ability to remove stains, a clean feeling in the mouth, less mouth odor and healthy gums.
A mixture of an approximately 60 percent sodium bicarbonate paste with a 3 percent solution of hydrogen peroxide has been used to treat periodontal disease. This method requires the user, immediately before use, to prepare the mixture in the palm of the hand. The mixture is then applied along the gum line. Due to the foaming action of the hydrogen peroxide, and because the mixture is prepared on the palm of the hand, this procedure is messy.
To overcome the inconvenience of the above procedure, various dentifrices have been formulated which contain oxidizing aqents such as sodium perborate (Cella, et al., U.S. Pat. No. 3,885,028 and Molnar, U.S. Pat. No. 2,275,979), potassium chlorate, urea peroxide (Gordon, U.S. Pat. No. 4,522,805 and Schaeffer, U.S. Pat. No. 4,528,180) and magnesium peroxide. Balsam, M.S. et al, Cosmetics: Science and Technology, Volume 1, Second Edition, Wiley Interscience (1972) page 496.
Sodium perborate and potassium chlorate do not release significant levels of hydrogen peroxide in water. Kirk-Othmer Encyclopedia of Chemical Technology, Third Edition, Volume 17, pages 1-22; Kern, D.M., J. Am. Chem. Soc. 77:5458, 1955. Although sodium perborate has been classified category 1 (Federal Register, Oct. 7, 1982) for temporary use as an oral wound cleaner, it is of questionable safety for frequent topical use on the mucous membranes of the mouth and throat because it contains boron which can undergo systemic absorption. (Federal Register Vol. 44 No. 214 page 63282, Fri., Nov. 2, 1979, Proposed Rules). Sodium perborate also has an undesirably low solubility in water of about 2.5%. This low solubility limits the concentration of oxidizing agent. Magnesium peroxide, an essentially insoluble salt in water, is similarly undesirable. Handbook of Chemistry and Physics, 59th Ed., 1978-79.
Various peroxide releasing dentifrice formulations utilize urea peroxide as the oxidizing agent. See U.S. Pat. No. 4,522,805. However, sodium bicarbonate/urea peroxide dentifrices are not stable, presumably because hydrogen peroxide solutions are not stable at alkaline pH (see "Hydrogen Peroxide," Schumb, Satterfield & Wentworth, American Chemical Society Monograph No. 128 (1955), pp. 526-530). As a result, dentifrice preparations have been proposed in which the urea peroxide and sodium bicarbonate components are placed in separate compartments of a container (see Schaeffer, U.S. Pat. No. 4,528,180, column 2, lines 4-9,). However, a uniform ratio of peroxide and bicarbonate in the formulation disclosed in Schaeffer is not assured. Further, where the two incompatible pastes are dispensed through a single nozzle, there is a possibility of reaction between the two pastes at the point at which they come in contact inside the tube.
Alkali and alkaline earth metal percarbonates, e.g., ammonium percarbonate, were also described as peroxide releasing agents for dentifrices more than 80 years ago. (Gane, U.S. Pat. No. 802,099 granted Oct. 17, 1905.) The percarbonates have not previously been used in dentifrice formulations, however, because of their high pH in solution which could cause severe gum irritation. One safe, palatable and convenient formulation containing sodium bicarbonate and sodium percarbonate in the form of a stable tooth powder has recently been described in U.S. Application Ser. No. 017,143, filed Feb. 20, 1987 and assigned to the owner of the present invention. However, no stable toothpaste or gel dentifrices are currently known, which combine sodium bicarbonate with sodium percarbonate.
It is accordingly among the objects of the present invention to provide a stable, peroxide releasing toothpaste and dentifrice gel. It is a further object of the invention to provide such a formulation which is useful in the treatment of periodontal disease and which minimizes dental caries, in a safe, more convenient and palatable form than embodied in any known prior art formulation.